Melt blown fiber forming process and method of making fibrous structures

ABSTRACT

A melt blowing process comprising: (a) providing a thermoplastic polymer material that includes at least one or a plurality of polyester polymers and at least one or a combination of different meltable metal phosphinates; and (b) melt blowing the thermoplastic polymer material into at least one fiber or a plurality of fibers, with each fiber having a diameter or thickness that is less than about 10 microns. The metal phosphinate is in an amount that (a) reduces the viscosity of the polyester polymer and (b) functions as a crystallizing agent, which at least promotes crystallization of the polyester polymer, when the thermoplastic polymer material is melt blown into the at least one fiber. Non-woven and woven fibrous structures can be made using fibers made from this process.

FIELD OF THE INVENTION

The present invention relates to processes for melt blowing polymerfibers, in particular to processes for melt blowing fibers comprising apolyester polymer, and more particularly to melt blowing such fibershaving a diameter or thickness that is less than about 10 microns. Thepresent invention also relates to such melt blown polymer fibers andfibrous structures made therefrom that exhibit low shrinkage, as well aspolymer compositions that are melt blowable into such fibers.

BACKGROUND

Melt blowing is an extrusion technology that produces fine fiber websdirectly from a polymer. In melt blowing, thermoplastic polymer streamsare extruded through a die containing closely arranged small orificesand attenuated by two convergent streams of high-velocity hot air intofine fibers. These fine fibers can be used to form a melt blown weboften referred as a blown micro-fiber web. Blown micro-fiber webs areused in a variety of applications including acoustic and thermalinsulation, filtration, barrier webs and wipes among many others. Theprimary resin used in blown micro-fiber processes is polypropylene (PP).

The present invention is an improvement over prior techniques for meltblowing polymer fibers, as well as melt blown fibers and fiber webs.

SUMMARY OF THE INVENTION

Before the present invention, it was difficult to melt blowthermoplastic polymer fibers comprising a polyester polymer, especiallysuch fibers having a diameter or thickness of less than about 10microns. To melt blow such fibers, the corresponding thermoplasticpolyester polymer has to be heated to temperatures much higher than itsmelting point. Such elevated heating of the thermoplastic polyesterpolymer can result in one or any combination of problems that caninclude, for example, excessive degradation of the polymer, weak andbrittle fiber webs, and formation of sand during meltblowing. Even whenmelt blown polyester polymer fibers are produced using conventionprocesses, fibrous webs and other fibrous structures made with suchfibers typically exhibit excessive shrinkage or otherwise poordimensional stability at temperatures equal to or above the glasstransition temperature of the polyester polymer used to make the fibers.

The present inventors have discovered a way to melt blow fibers using athermoplastic polymer comprising at least one polyester polymer or aplurality of polyester polymers, where the fibers can be suitable foruse at temperatures equal to or above the glass transition temperatureof the polyester polymer used to make the fibers, even when the diameterof the fibers is less than about 10 microns. Such fibers may exhibit oneor more desirable properties including, for example, one or anycombination of: relatively low cost (e.g., manufacturing and/or rawmaterial costs), durability, reduced shrinkage from heat exposure,increased dimensional stability at elevated temperature, and flameretardant properties. The present invention can also be used to provideenvironmentally friendlier non-halogenated flame retardant polyesterbased nonwoven or woven fibrous materials.

The present invention includes a process for making dimensionally stablemelt blown micro-fibrous structures (e.g., mats, webs, sheets, scrims,fabric, etc.) with fibers comprising, consisting essentially of, orconsisting of one or a combination of polyester polymers. Because theyare made with polyester containing polymer materials that aredimensionally stable at elevated temperatures, non-woven and wovenfibrous structures (e.g., mats, webs, sheets, scrims, fabric, etc.) madewith such fibers, and articles (e.g., thermal and acoustic insulationand insulating articles, liquid and gas filters, garments, and personalprotection equipment) made from such fibrous structures, can be used inrelatively high temperature environments while exhibiting only minor, ifany, amounts of shrinkage. The development of dimensionally stablepolyester blown micro-fiber webs, which will not shrink significantlyupon exposure to heat, will widen the applicability of these webs. Bybeing made to exhibit sufficient flame retardant properties and/ordurability, in addition to shrink resistance, such melt blownmicro-fiber webs can become particularly useful as thermal andacoustical insulation.

In accordance with one aspect of the present invention, a process isprovided that comprises: (a) providing a thermoplastic polymer materialcomprising at least one or a plurality of polyester polymers and atleast one or a combination of different meltable metal phosphinates; (b)melt blowing the thermoplastic polymer material into at least one fiberor a plurality of fibers; and (c) heating the at least one fiber to atemperature equal to or above the glass transition temperature (T_(g))of the polyester polymer. The metal phosphinate is in an amount thataccelerates, induces or at least promotes crystallization of thepolyester polymer, when the thermoplastic polymer material is melt blowninto the at least one fiber. The polyester polymer of the at least onefiber is at least partially crystalline.

In accordance with an additional aspect of the present invention, aprocess is provided that comprises: (a) providing a thermoplasticpolymer material that includes at least one or a plurality of polyesterpolymers and at least one or a combination of different meltable metalphosphinates; and (b) melt blowing the thermoplastic polymer materialinto at least one fiber or a plurality of fibers, with each fiber havinga diameter or thickness that is less than about 10 microns. The metalphosphinate is in an amount that (a) reduces the viscosity of thepolyester polymer and (b) functions as a crystallizing agent, whichaccelerates, induces or at least promotes crystallization of thepolyester polymer, when the thermoplastic polymer material is melt blowninto the at least one fiber. The polyester polymer of the at least onefiber is at least partially crystalline.

In another aspect of the present invention, a method of making anon-woven or woven fibrous structure (e.g., a mat, sheet, scrim, web,fabric, etc.) is provided, where the method comprises making fibersusing the melt blowing process according to the present invention andforming the fibers into a non-woven or woven fibrous structure.

In an additional aspect of the present invention, at least one or moremelt blown fibers are provided where each fiber has a diameter of lessthan about 10 microns and comprises a thermoplastic polymer materialcomprising at least one or a plurality of polyester polymer and at leastone or a combination of different meltable metal phosphinates. While a100% crystalline polyester polymer may theoretically be possible, as apractical matter, some portion of the polymer structure will remainamorphous. Thus, the polyester polymer used in these fibers issemi-crystalline. That is, at least a desired minimum percentage of thepolyester polymer is crystalline. The minimum percentage ofcrystallinity desired will depend upon the particular fiber application.

In another aspect of the present invention, a fibrous structure isprovided that comprises a plurality of the melt blown fiber according tothe present invention. The fibrous structure can be non-woven, woven, ora combination thereof.

In an additional aspect of the present invention, a fibrous structure isprovided that comprises a plurality of melt blown fibers. Each meltblown fiber comprises a thermoplastic polymer material comprising atleast one polyester polymer, or a plurality of polyester polymers, andat least one or a combination of different meltable metal phosphinates.The at least one polyester polymer is at least partially crystalline,and the fibrous structure is operatively adapted (e.g., structurallydimensioned, shaped, or otherwise configured or designed) for use in anenvironment (e.g., adjacent an internal combustion engine, etc.) wherethe fibrous structure is exposed to temperatures equal to or above theglass transition temperature of the at least one polyester polymer.

In a further aspect of the present invention, a low shrinkagethermoplastic polymer composition is provided that comprises at leastone or a plurality of polyester polymers and less than or equal to about2% by weight of at least one or a combination of different meltablemetal phosphinates.

The above and other aspects and advantages of the present invention arefurther shown and described in the drawings and detailed description ofthis invention, where like reference numerals are used to representsimilar parts. It is to be understood, however, that the drawings anddescription are for illustration purposes only and should not be read ina manner that would unduly limit the scope of this invention.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In a number of places in this application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1a is an 1800× photomicrograph of a fibrous structure embodiment inaccordance with the present invention, where the thermoplastic polymermaterial of the fibers comprises about 2.5% by weight of a meltablemetal phosphinate;

FIG. 1b is an 1800× photomicrograph of a fibrous structure embodiment inaccordance with the present invention, where the thermoplastic polymermaterial of the fibers comprises about 5% by weight of a meltable metalphosphinate;

FIG. 1c is an 1800× photomicrograph of a fibrous structure embodiment inaccordance with the present invention, where the thermoplastic polymermaterial of the fibers comprises about 10% by weight of a meltable metalphosphinate;

FIG. 2a is a front view of a fibrous web wound into a roll in accordancewith the present invention;

FIG. 2b is a top view of a sheet or mat cut from the fibrous web of FIG.2 a;

FIG. 2c is a 450X photomicrograph of a cross-section of the fibrous webof FIG. 2 a;

FIGS. 2d is a 450X photomicrograph of the surface of the fibrous web ofFIG. 2 a.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

In describing preferred embodiments of the invention, specificterminology is used for the sake of clarity. The invention, however, isnot intended to be limited to the specific terms so selected, and eachterm so selected includes all technical equivalents that operatesimilarly.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

The term “polymer” will be understood to include polymers, copolymers(e.g., polymers formed using two or more different monomers), oligomersand combinations thereof, as well as polymers, oligomers, or copolymersthat can be formed in a miscible blend.

The terms “comprising”, “comprises”, “including” and variations thereofdo not have a limiting meaning where these terms appear in thedescription and claims.

The words “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably and encompass embodiments having plural referents,unless the content clearly dictates otherwise. Thus, for example, a meltblown fiber that comprises “a” polyester polymer can be interpreted tomean that the fiber includes “one or more” polyester polymers.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements (e.g., preventingand/or treating an affliction means preventing, treating, or bothtreating and preventing further afflictions).

As used herein, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

In a melt blowing process according to the present invention, athermoplastic polymer material is provided that comprises at least oneor a plurality of polyester polymers (such as, e.g., PET, PBT, PLA andpossibly PHB and PTT) and at least one meltable metal phosphinate or acombination of different meltable metal phosphinates. This thermoplasticpolymer material is melt blown into a plurality of fibers, with eachfiber having a diameter or thickness that is less than about 10 microns.

It can be commercially desirable for the fiber diameter to be less thanor equal to about 9, 8, 7, 6 or even 5 microns or less. It can even becommercially desirable for the fiber diameter to be 4, 3, 2 or 1 micronor smaller. The metal phosphinate is present in an amount that reducesthe viscosity of the one or more polyester polymers, and possibly otherpolymers, used so that the thermoplastic polymer material can be meltblown into such size fibers at a temperature of less than or equal toabout 370° C., and preferably at a temperature of less than or equal toabout 360° C. It can be desirable for the metal phosphinate content tobe an amount that allows the thermoplastic polymer material to be meltblown into such size fibers at a temperature of less than or equal toabout 350° C., 340° C. 330° C., 320° C., 310° C., or even less than orequal to 300° C. There is also enough metal phosphinate to function as acrystallizing agent that accelerates, induces or at least promotescrystallization of the polyester polymer, when the thermoplastic polymermaterial is melt blown into the at least one fiber. There is a meltblowing temperature at which a polymeric material will begin to degrade(i.e., their degradation temperature). For example, the onset of PETdegradation is about 380° C. Melt blown polymeric fibers can stillexhibit problems, when heated to below such a degradation temperature,For example, PET can exhibit problems such as “sand out” when thepolymer is melt blown at temperatures above about 350° C.

The melt blowing should be performed within a range of temperatures hotenough to enable the thermoplastic polymer material to be melt blown butnot so hot as to cause unacceptable deterioration of the thermoplasticpolymer material. For example, the melt blowing can be performed at atemperature that causes the thermoplastic polymer material to reach atemperature in the range of from at least about 290° C. to less than orequal to about 360° C., 350° C., 340° C., 330° C., 320° C., 310° C., or300° C.

In the melt blowing process, the thermoplastic polymer material ismelted to form a molten polymer material. The melt blowing process caninclude forming (e.g., extruding) the molten polymer material into atleast one or a plurality of fiber preforms and solidifying (e.g.,cooling) the at least one fiber preform into the at least one fiber. Thethermoplastic polymer material can still be molten when the perform isfirst made. It is desirable for the metal phosphinate to melt at orbelow the melting point of at least the polyester polymer and functionas a crystallization promoter or crystallizing agent that causes atleast the polyester polymer phase of the molten polymer material tocrystallize before, or at least about the same time as, the moltenpolymer material solidifies (i.e., as the fiber preform solidifies intothe fiber).

The metal phosphinate promotes faster crystallization of the solidifyingmolten polyester polymer. As a result, the melt blown fiber and anon-woven web of the fibers will exhibit a reduction in heat inducedshrinkage. This reduction in shrinkage is especially evident with regardto the length and width dimension of a fiber web made with the fiber.The use of the metal phosphinate may actually improve the mechanicalproperties of the melt blown fiber, if the metal phosphinate is used inan amount equal to or less than about 10%.

As used herein, a metal phosphinate includes phosphinate metal salt(s).Metal phosphinates may include, e.g., zinc, aluminum and calciumphosphinates, and preferably zinc phosphinates, such as those disclosedin U.S. Pat. Nos. 6,365,071, and 6,255,371; U.S. Patent Publication No.US2004/0176506, which are incorporated herein by reference in theirentirety. In addition, depending on the particular polyester polymerused (e.g., PET), a fiber thickness of 10, 9, 8, 7, 6, or 5 microns isequivalent to about 1.0, 0.8, 0.6, 0.5, 0.4, or 0.3 denier,respectively.

In accordance with how it is used in this invention and for at least thepolymer composition so far tested, it is believed that the metalphosphinate will only sufficiently reduce the viscosity of the polyesterpolymer composition (i.e., allow the composition to be melt blown intosuch small diameter fibers), when about 20% or less of the metalphosphinate is used. It has been found that a melt blown polyesterpolymer will crystallize to some degree without the metal phosphinatebeing present, but not fast enough. Without the metal phosphinate, notenough of the polyester polymer crystallizes to prevent significant heatinduced shrinkage of the melt blown polyester polymer. While notintending to be bound by theory, it is believed that the metalphosphinate may accelerate, induce or at least promote crystallizationof the polyester polymer by causing a more rapid nucleation of thepolyester polymer after being melt blown.

The step of providing a thermoplastic polymer material can comprise meltblending of the metal phosphinate with the polyester polymer. Thepolyester is in polymer form when melt blended with the metalphosphinate. In addition, the step of melt blowing can comprise directlyextruding the thermoplastic polymer material through at least one or aplurality of corresponding die openings designed (e.g., dimension andshaped) so as to form the at least one fiber. The melt blown fibers canbe formed into a non-woven fiber web by the use of conventiontechniques. For example, the non-woven fiber web could be formed byallowing the melt blown fibers to self-bond or stick to each other as aresult of being still warm from the extrusion process. The melt blownfibers may also be bonded together, to form the non-woven fiber web, byusing calender rolls (e.g., while the fibers are still warm and/or afterthe fibers have cooled down), heated air, adhesive coating(s),mechanical bonding techniques, or any combination thereof.

The thermoplastic polymer material can comprise a blend of a polyesterpolymer and at least one other polymer to form a polymer blend of two ormore polymer phases. It can be desirable for the polyester polymer to bean aliphatic polyester, aromatic polyester or a combination of analiphatic polyester and aromatic polyester. The thermoplastic polymermaterial can comprise at least about 0.1, 0.2, 0.3, 0.4, or 0.5 percentby weight of the metal phosphinate. It can be desirable for thethermoplastic polymer material to comprise less than about 20 percent byweight of the metal phosphinate. At concentrations above about 20percent, the metal phosphinate becomes less effective as acrystallization promoter. Also at such high metal phosphinateconcentrations, the viscosity of the melt blended polyester polymer andmetal phosphinate will increase, thereby disrupting the ability of thethermoplastic polymer material to be melt blown into fibers. Thisincrease in viscosity can make it impossible, or at least difficult, tomelt blow small diameter fibers having a diameter of 10 microns or less.

The polyester polymer can form the only, a majority, or at least asubstantial polymer portion or phase of the thermoplastic polymermaterial. The polyester polymer forms a substantial portion of thethermoplastic polymer material, when the thermoplastic polymer materialcan be melt blown and the resulting fiber(s) exhibits acceptablemechanical properties and thermal properties. For example, a polyesterpolymer content of at least about 70% by volume can form a substantialpolymer portion or phase of the thermoplastic polymer material.Acceptable mechanical properties or characteristics can include, e.g.,tensile strength, initial modulus, thickness, etc. The fiber can be seenas exhibiting acceptable thermal properties, e.g., when a non-woven webmade from the fibers exhibits less than about 30, 25, 20 or 15 percent,and preferably less than or equal to about 10 or 5 percent, linearshrinkage when heated to a temperature of about 150° C. for about 4hours.

After the melt blowing, the polyester polymer phase of the thermoplasticpolymer material is completely, mostly, partially, or at leastsubstantially crystalline and the remainder of the polyester polymer isamorphous. As used herein, the polyester polymer phase can be seen asbeing substantially crystalline, when enough of the polyester polymercrystallizes that a non-woven web made of the melt blown fibers exhibitsless than about 30, 25, 20 or 15 percent linear shrinkage, andpreferably less than or equal to about 10 or 5 percent linear shrinkage,when heated to a temperature of about 150° C. for about 4 hours. Linearshrinkage is the average of the machine and cross direction webshrinkage.

Not intending to be so limited, it has been found that commerciallyacceptable properties (e.g., low web shrinkage) can be obtained byproviding (a) a thermoplastic polymer material that comprises a minimumof about 70%, and preferably about 80%, by weight of a polyester and (b)for a minimum of about 30%, and preferably about 35%, by mass (asmeasured by Differential Scanning Calorimetry) of the thermoplasticpolymer material forming the fiber to be crystalline. It can becommercially significant for a web made with fibers according to thepresent invention to exhibit heat induced shrinkage of less than 10%. Itis believed that commercially significant fibers, according to theinvention, may be obtainable using a thermoplastic polymer materialcomprising a minimum of at least about 90%, 85%, 80%, 75% or even 70% byweight of a polyester, with varying degrees of crystallinity.

The thermoplastic polymer material of a fiber that is melt blownaccording to the present invention can exhibit a low molecularorientation and/or different crystal morphology, when compared to amelt-spun or spunbond fiber made with the same thermoplastic polymermaterial. A melt blown fiber made according to the present invention canexhibit a birefringence of less than or equal to about 0.10, 0.09, 0.08,0.07, 0.06, 0.05, 0.04, 0.03, 0.02 or 0.01. The birefringence of thefiber is related to the level of polymer molecular orientation presentin the fiber. To some extent, birefringence may also be used to measurethe degree of crystallization (i.e. volume of crystal structure) in thefiber.

Non-woven and woven fibrous structures (e.g., a scrim, web, mat, sheet,fabric, etc.) can be made according to the present invention by makingfibers using a melt blowing process disclosed herein and forming thefibers into a non-woven or woven fibrous structure. The following aredescriptions or citations to references that describe differenttechniques that may be used to form the inventive melt blown microfibersinto a non-woven web or other fibrous structure, as well as those thatmay be used to form the melt blown microfibers into a woven web or otherfibrous structure. For example, the concept of meltblowing fibers wasfirst demonstrated by V. A. Wente in “Manufacture of Superfine OrganicFibers.”, U.S. Department of Commerce, Office of Technical ServicesReport No. PBI 11437, Naval Research Laboratory, Report 4364, 1954, andin “Superfine Thermoplastic Fibers” Industrial and EngineeringChemistry, 48: 1342-1346, 1956. Methods of incorporating particulates orfibers, such as staple fibers, bulking fibers or binding fibers, can beused with the method of forming melt-blown microfiber webs disclosed,for example, in U.S. Pat. Nos. 4,118,531; 4,429,001 or 4,755,178, whereparticles or fibers are delivered into a single stream of melt-blownfibers. In addition, U.S. Pat. No. 3,971,373 teaches how to incorporateparticulates (fibers) into a double stream of meltblown fibers.

A melt blown fiber according to the present invention can have adiameter or thickness that is less than about 10 microns, or less thanor equal to about 9, 8, 7 or 6 microns. The melt blown fiber can alsocomprises a thermoplastic polymer material comprising at least one or aplurality of polyester polymers (such as, e.g., PET, PBT, PLA, andpossibly PHB and PTT) and at least one or a combination of differentmeltable metal phosphinates. The polyester polymer is at leastsubstantially crystalline. That is, at least a substantial amount of thestructure of the polyester polymer is in a crystalline form. It may bedesirable for the polyester polymer to be at least about 30% by masscrystalline and preferably in the range of from about 30% to about 70%,or in the range of from about 35% to about 65%, crystalline by mass.

The thermoplastic polymer material used to make the present melt blownfibers can comprises a blend of the polyester polymer and at least oneother polymer to form a polymer blend. The polyester polymer can be analiphatic polyester, aromatic polyester or a combination of an aliphaticpolyester and aromatic polyester. The polyester polymer forms (a) theonly polymer phase or all of the thermoplastic polymer material, (b) amajority of polymer phase or a major portion of the thermoplasticpolymer material, or (c) at least a substantial portion of the polymerphase or the thermoplastic polymer material. While all, most, or atleast a substantial portion of the polyester polymer phase of thethermoplastic polymer material is crystalline, the remainder of thepolyester polymer is amorphous. Enough of the polyester polymercrystallizes that a non-woven web comprising a plurality of the meltblown fibers exhibits less than about 30, 25, 20 or 15 percent, andpreferably less than or equal to about 10 or 5 percent, linear shrinkagewhen heated to a temperature of about 150° C. for about 4 hours.

The thermoplastic polymer material can comprises about 20 percent byweight or less of the metal phosphinate. If more than 20% of the metalphosphinate is used, fiber formation is disrupted, thereby making itdifficult to spin the fibers. It can be desirable for the thermoplasticpolymer material to comprise at least about 0.1, 0.2, 0.3, 0.4, or 0.5percent by weight of the metal phosphinate. The metal phosphinate can bea zinc phosphinate.

The melt blown fiber can exhibit a low molecular orientation whencompared to a melt-spun or spunbond fiber made with the same polymermaterial. In addition, the melt blown fiber can exhibit a birefringenceof less than or equal to about 0.01. The birefringence of the fiber isrelated to the level of polymer molecular orientation present in thefiber.

While meltable metal phosphinates are used to impart flame retardantcharacteristics to polymer materials, a low shrinkage thermoplasticpolymer composition according to the present invention can include atleast one or a plurality of polyester polymers combined with an amountof at least one or a combination of different meltable metalphosphinates, where the amount of the metal phosphinate(s) would not beenough to make the composition sufficiently flame retardant, forcommercial purposes, but the amount is enough so as to accelerate,induce or at least promote crystallization of the polyester polymer(s),when the thermoplastic polymer material is melt blown into a fiber. Forexample, some such compositions may not exhibit commercially acceptableflame retardant characteristics in an amount of less than or equal toabout 2% by weight of at least one or a combination of differentmeltable metal phosphinates. At the same time, such a low shrinkagethermoplastic polymer composition can comprise a minimum amount of atleast one or a combination of different meltable metal phosphinates thatwould be needed to allow the composition to be melt blown into fibershaving a diameter of less than about 10 microns and still besufficiently crystalline to exhibit low shrinkage at elevatedtemperature. It has been found that some such compositions can be meltblown into such fibers, if they contained at least about 0.5% by weightof the at least one meltable metal phosphinate. In one exemplaryembodiment, fibers having a diameter of less than about 10 microns havebeen successfully melt blown using compositions having a polymercomponent that is 100% by weight polyester and at least about 0.5% byweight of the at least one meltable metal phosphinate. It is believedthat this amount of meltable metal phosphinate (i.e., about 0.5% byweight) may also be the minimum amount of metal phosphinate needed tomelt blow 10 micron diameter fibers, even when the polymer component ofthe composition contains in the range of from less than 100% by weightpolyester to the desired minimum amount of polyester (i.e., about 90%,85%, 80%, 75%, or even 70% by weight).

Referring to FIGS. 1a -1 c, melt blown fibers 10 according to thepresent invention can be in the form of a fibrous structure 12 (e.g., aweb, scrim, mat, sheet, fabric, etc.), which can be non-woven, woven ora combination thereof. The thermoplastic polymer material of the fibers10 of the FIG. 1a embodiment comprises about 2.5% by weight of the zincdiethylphosphinate sold under the name Exolit™ OP 950 and manufacturedby Clariant International Ltd., which is located at Rothausstrasse 61,4132 Muttenz, Switzerland, with the remainder of the fiber compositionbeing the polyethylene terephthalate (PET) type 8416. The thermoplasticpolymer material of the fibers 10 of the FIG. 1b embodiment comprisesabout 5% by weight of the Exolit™ OP 950, with the remainder being thePET type 8416. The thermoplastic polymer material of the fibers 10 ofthe FIG. 1c embodiment comprises about 10% by weight of the Exolit™ OP950, with the remainder being the PET type 8416. At 10% loadings andabove, the Exolit™ OP 950 tends to cluster up and become difficult todistribute and disperse within the fiber cross-section, as indicated byreference number 14. It has also been shown that higher loadings of theExolit™ OP 950 (10 wt % and above) may require pre-compounding of theresin with the zinc phosphinate prior to making the fibers.

A fibrous structure according to the present invention can furthercomprise at least one or a plurality of other types of fibers (notshown) such as, for example, staple or otherwise discontinuous fibers,melt spun continuous fibers or a combination thereof. Referring to FIGS.2a-2d , the present inventive fibrous structures 12 can be formed, forexample, into a non-woven web 20 that can be wound about a tube or othercore 22 to form a roll 24 (see FIG. 2a ) and either stored forsubsequent processing or transferred directly to a further processingstep. The web 20 may also be cut into individual sheets or mats 24directly after the web 20 is manufactured or sometime thereafter. Theweb 20 can be used to make any suitable article 20 such as, for example,thermal and/or sound insulation components for vehicles (e.g., trains,airplanes, automobiles and boats). Other articles such as, for example,bedding, shelters, tents, insulation, insulating articles, liquid andgas filter, wipes, garments and garment components, personal protectiveequipment, respirators, etc. can also be made using fibrous structuresaccording to the present invention. FIG. 2c shows a cross section of theweb 20, and FIG. 2d shows an exposed surface of the web 20.

The following Examples have been selected merely to further illustratefeatures, advantages, and other details of the invention. It is to beexpressly understood, however, that while the Examples serve thispurpose, the particular ingredients and amounts used as well as otherconditions and details are not to be construed in a manner that wouldunduly limit the scope of this invention.

Test Methods Mechanical Properties of Melt Blown Fiber Nonwoven Webs

The break force and elastic modulus of the meltblown webs weredetermined using Instron tensile machine equipped with pneumatic clamps,according to ASTM D5035-06. Five specimens were cut from each web samplein both the machine direction (MD) and cross direction (CD). Thethickness of each specimen was measured with a caliper gauge. Thedimensions of the specimens were 2.54 cm wide by 15.24 cm long (1 in.×6in.). A gage length of 7.62 cm (3 inches) and a crosshead testing speedof 30.48 cm/min (12 inches/min.) were used. Values for the break forceand modulus for both the machine and cross direction were obtained andaveraged for the five replicates (specimens) and are reported in Table 1below.

TABLE 1 Break Break Elastic Elastic Force (N) Force (N) Modulus ModulusExample MD CD (Pa) MD (Pa) CD 1 16.6 18.3 4.2 × 10⁵ 6.8 × 10⁴ 2 13.018.7 3.0 × 10⁵ 1.8 × 10⁵ 3 23.3 19.4 3.4 × 10⁵ 2.7 × 10⁵ C1 9.3 12.4 2.4× 10⁵ 1.5 × 10⁴

Flame Retardant Properties of Melt Blown Fiber Nonwoven Webs

The flame retardant characteristics of the meltblown webs weredetermined using ASTM D6413-08. Ten specimens (76 mm by 300 mm) were cutfrom each web sample in both the machine direction (MD) and crossdirection (CD). Values for char length and after-flame time weredetermined and are reported in Table 2 below. The ten MD and ten CDspecimens were averaged together. Occurrence of any web flaming dripswas also reported. After-flame time is defined as the length of the timefor which material continues to flame after the ignition source has beenremoved. Char length is defined as the distance from the material edgedirectly exposed to the flame to the furthest point of visible materialdamage after a 100 gram tearing force has been applied.

TABLE 2 Char Length After-flame Flaming Drips Example (mm) time (sec)(Yes/No) 1 65.2 0 No 2 72.2 0 No 3 94.6 0 No C1 102.4 44.5 Yes

Field Emission Scanning Electron Microscope (FESEM)

The meltblown webs were imaged and photographed on a Hitachi 54700 fieldemission scanning electron microscope (FESEM) using low voltage in theExB compositional mode at magnifications of 250× and 1000×.Cross-sectional specimens of each web were prepared by fracturing eachweb sample under liquid nitrogen with a new surgical blade. Thespecimens were then attached to an FESEM stub with carbon conductivetape and compositional images were then taken. ExB images are createdusing backscattered electrons which are generally more affected bycomposition, thus areas of higher average atomic number appear brighterin the ExB images. Each specimen was imaged in several areas to obtainrepresentative images of the samples. Representative images are shown inFIGS. 1 a, 1 b, 1 c, 2 c and 2 d.

Modulated Differential Scanning Calorimetry (MDSC)

Thermal characteristics of the neat type 8396 PET resin and a blend oftype 8396 with 2.5 wt % zinc diethylphosphinate (ZDP) were measuredusing a TA Instruments Q2000 Modulated Differential Scanning Calorimeter(MDSC). The test sample was prepared by melting the 8396 PET resin in aBrabender mixer. The molten resin was removed and air cooled at roomtemperature. A blend of the type 8396 with ZDP was prepared in the samemanner except the ZDP was added to the Brabender after the PET wascompletely melted and then mixed. Specimens were weighed and loaded intoTA Instruments T_(zero) aluminum pans. A linear heating rate of 4°C./min. was applied with a perturbation amplitude of ±0.636° C. every 60seconds. The specimens were subjected to a short hold to dry thespecimen followed by a heat (H1)—quench cool (Q)—heat (H2)—slow cool(C2)—heat (H3) profile over a temperature range of 0 to 290° C. Theglass transition temperatures were evaluated using the step change inthe heat flow (HF) or non-reversing (NR) heat flow curves. The onset,midpoint (half height), and end temperatures of the transition werenoted as well as the change in heat capacity observed at the glasstransition. Peak integrations were evaluated using the heat flow (HF),reversing (R) heat flow, or non-reversing (NR) heat flow signals. Thepeak onset temperature, the peak minimum or maximum temperature, and thepeak area results were noted. Peak integration results were normalizedfor sample weight and reported in J/g. The specimen degree ofcrystallinity was calculated according to the equation:

$\chi = {{\frac{\Delta \; H_{fs}}{\Delta \; H_{fcr}} \cdot 100}\%}$

where χ is the degree of crystallinity of a material; ΔH_(fs) is theheat of fusion of a polymer material; ΔH_(fcr) is the theoretical heatof fusion of a 100% crystalline material. A value of 140 J/g wasutilized for evaluating the specimens. Thermal values are reported inTable 3 below. T_(cc) is the cold crystallization peak temperature.ΔH_(cc) is the area under the cold crystallization peak. T_(m) is themelting point temperature. ΔH_(m) is area under the melting peak. T_(c)is the crystallization peak temperature (cooling cycle). ΔH_(c) is areaunder the crystallization peak.

TABLE 3 Slow Cool 2^(nd) Heat Scan after Quench after 2^(nd) Heat ScanExam- T_(cc) ΔH_(cc) T_(m) ΔH_(m) χ T_(c) ΔH_(c) ple (° C.) (J/g) (° C.)(J/g) (%) (° C.) (J/g) 5 125 0.6 258 50 35 220 50 C3 139 24 258 45 15208 46

Shrinkage Measurements

The shrinkage properties of the meltblown webs were calculated for eachweb sample using three 10 cm by 10 cm specimens in both the machine (MD)and cross direction (CD). The dimensions of each specimen was measuredbefore and after their placement in a Fisher Scientific Isotemp Oven at80° C. for 60 minutes, 150° C. for 60 minutes, and 150° C. for 7 days.Shrinkage for each specimen was calculated in the MD and CD by thefollowing equation:

${\% \mspace{14mu} {Shrinkage}} = {\left( \frac{L_{O} - L}{L_{O}} \right) \times 100\%}$

where L₀ is the initial specimen length and L is the final specimenlength. Average values of shrinkage were calculated and reported inTable 4 below.

TABLE 4 60 minutes 60 minutes 7 days at 80° C. at 150° C. at 150° C. % %% % % % Exam- Shrink Shrink Shrink Shrink Shrink Shrink ple (CD) (MD)(CD) (MD) (CD) (MD) 1 1.3 1.3 1.3 1.3 2.0 2.0 2 1.0 1.0 1.3 1.0 1.3 1.03 0.0 0.0 1.0 1.0 1.0 1.0 C1 6.3 9.0 31.0 32.3 30.3 32.7 4 0.0 0.0 1.01.0 Not Not Tested Tested C2 5.0 5.0 28.0 22.0 Not Not Tested Tested

EXAMPLES Materials Used

Polyethylene terephthalate (PET) type 8416: commercially available fromInvista of Wilmington, Del., melting point of 260° C. and intrinsicviscosity of 0.51 dL/g.

Polyethylene terephthalate (PET) type 8396: commercially available fromInvista of Wilmington, Del., melting point of 260° C. and intrinsicviscosity of 0.55 dL/g.

Zinc diethylphosphinate: commercially available under the tradedesignation EXOLIT™ OP950 from Clariant International of Muttenz,Switzerland, melting point of 220° C., degradation temperature (definedat 2% weight loss) of 380° C. and phosphorous content of approximately20%.

Example 1

A PET meltblown microfiber web of the present invention was preparedusing type 8416 PET resin and EXOLIT™ OP950 additive using the followingprocedure. A masterbatch of the 8416 PET (97.5 wt %) and EXOLIT™ OP950additive (2.5 wt %) was prepared using an Ultra Glide 25 mm twin-screwextruder (Krass Maffei Kumstofftechnik-Berstorff, Munich Germany)(co-rotating, with ten zones) using a melt temperature of 280° C. Themasterbatch was pelletized using a conventional strand die/watertrough/pelletizer apparatus. The masterbatch pellets were then extrudedinto microfiber webs by a process similar to that described in Wente,Van A., “Superfine Thermoplastic Fibers” in Industrial EngineeringChemistry, Vol. 48, pages 1342 et seq (1956), or in Report No. 4364 ofthe Naval Research Laboratories, published May 25, 1954 entitled“Manufacture of Superfine Organic Fibers” by Wente, Van. A. Boone, C.D., and Fluharty, E. L. except that a 31 mm (0.75 in.) Brabender conicaltwin screw extruder was used to feed the molten masterbatch compositionto a melt pump (65 rpm) and then to a 25 cm (10 inch) width meltblowingdie having orifices (10 orifices/cm) and orifice diameter of 381 microns(0.015 inch). The melt temperature was 290° C., the screw speed was 120rpm, the die was maintained at 290° C., the primary air temperature andpressure were, respectively, 350° C. and 60 kPa (8.7 psi), the polymerthroughput rate was 5.44 Kg/hr. (12 lbs/hr.), and the collector/diedistance was 15.2 cm (6 in.). The resulting nonwoven web had an averagefiber diameter of 8.9 microns and a basis weight of 149 g/m². Thenonwoven web was tested for shrinkage, mechanical and flame retardancyproperties as described above and are reported in Tables 1-3 above. AFESEM image of a cross-section of the web is shown in FIG. 1 a.

Example 2

A PET meltblown microfiber web was made as in Example 1 above except 5wt % of zinc diethylphosphinate (ZDP) was compounded into the type 8416PET resin and the melt pump speed was 70 rpm. The primary airtemperature and pressure were, respectively, 350° C. and 48 kPa (7 psi).The resulting nonwoven web had an average fiber diameter of 9.0 micronsand a basis weight of 166 g/m². The nonwoven web was tested forshrinkage, mechanical and flame retardancy properties as described aboveand are reported in Tables 1-3 above. A FESEM image of a cross-sectionof the web is shown in FIG. 1 b.

Example 3

A PET meltblown microfiber web was made as in Example 1 above except 10wt % of ZDP was compounded into the type 8416 PET resin and the meltpump speed was 50 rpm. The primary air temperature and pressure were,respectively, 350° C. and 62 kPa (9 psi). The resulting nonwoven web hadan average fiber diameter of 10.4 microns and a basis weight of 163g/m². The nonwoven web was tested for shrinkage, mechanical and flameretardancy properties as described above and are reported in Tables 1-3below. A FESEM image of a cross-section of the web is shown in FIG. 1 c.

Example 4

A PET meltblown microfiber web was made as in Example 3 above excepttype 8396 PET resin was used and a melt temperature of 290° C. was usedto prepare the masterbatch pellets. The pellets were extruded intomicrofiber webs as described in Example 1 above except the primary airtemperature and pressure were, respectively, 350° C. and 69 kPa (10psi). The resulting nonwoven web had an average fiber diameter of 10microns and a basis weight of approximately 153 g/m². The nonwoven webwas tested for shrinkage properties as described above and is reportedin Table 4 above.

Example 5

A PET compound for MDSC testing was prepared by using a Brabender mixerand melting the 8396 PET resin at 270° C. and 70 rpm screw speed for 2minutes. 2.5 wt % of ZDP was added to the Brabender, after the PET wascompletely melted, and then mixed for an additional two minutes at 70rpm and at 270° C. The molten blend was removed and air cooled at roomtemperature. The compound was tested for its thermal properties and theresults are reported in Table 3.

Comparative Example C1

As a comparative example a PET meltblown microfiber web was made as inExample 1 above except no ZDP was used. The primary air temperature andpressure were, respectively, 350° C. and 63 kPa (9.1 psi). The resultingnonwoven web had an average fiber diameter of 12.9 microns and a basisweight of 147 g/m². The nonwoven web was tested for shrinkage,mechanical and flame retardancy properties as described above and arereported in Tables 1-3 above.

Comparative Example C2

As a comparative example a PET meltblown microfiber web was made as inExample 4 above except no ZDP was used. The primary air temperature andpressure were, respectively, 350° C. and 63 kPa (9.1 psi). The resultingnonwoven web had an average fiber diameter of 12.9 microns and a basisweight of approximately 148 g/m². The nonwoven web was tested forshrinkage properties as described above and is reported in Table 4above.

Comparative Example C3

As a comparative example, a PET compound for MDSC testing was preparedby using a Brabender mixer and melting the 8396 PET resin at 270° C. and70 rpm screw speed for 2 minutes. The molten polymer then was removedand air cooled at room temperature. The polymer was tested for itsthermal properties and the results are reported in Table 3.

Table 4 demonstrates that the Example 1-4 fiber webs, which were loadedwith zinc diethylphosphinate, showed essentially no shrinkage incomparison to the Comparative Examples C1 and C2, which were 100% PETblown micro-fiber webs. Also, the ratio of metal phosphinate present inthe PET fiber of the web did not affect web shrinkage in general. The100% PET web described in Comparative Example C2 and made of higherintrinsic viscosity resin (type 8396) had overall lower shrinkage valuesthan the 100% PET web shown in Comparative Example C1. It is theorizedthat the addition of the metal phosphinate acts as a crystal nucleatingagent for the PET, increasing the crystallization rate and perhapsimproving its overall crystallinity. To verify this assumption, thermalscans for 100% PET type 8396 original resin and a blend of PET resinwith 2.5% zinc diethylphosphinate (Examples C3 and 5, respectively) werecollected and the results are shown in Table 3.

Exemplary Embodiments Melt Blowing Process Embodiments

-   1. A process comprising:

(a) providing a thermoplastic polymer material comprising at least oneor a plurality of polyester polymers and at least one or a combinationof different meltable metal phosphinates;

(b) melt blowing the thermoplastic polymer material into at least onefiber or a plurality of fibers; and

(c) heating the at least one fiber to a temperature equal to or abovethe glass transition temperature (T_(g)) of the polyester polymer (e.g.,a temperature that is at least about 5° C., 10° C., 15° C., 20° C., 25°C., or even 30° C. above the T_(g)),

wherein the metal phosphinate is in an amount that accelerates, inducesor at least promotes crystallization of the polyester polymer, when thethermoplastic polymer material is melt blown into the at least onefiber, and the polyester polymer of the at least one fiber is at leastpartially crystalline. The T_(g) of a typical polyester polymer, such aspolyethylene terephthalate (PET), is in the range of from about 80° C.to about 90° C.

-   2. The process according to embodiment 1, wherein the heating of the    at least one fiber is to a temperature that is at least about 5° C.,    10° C., 15° C., 20° C., 25° C., or even 30° C. above the T_(g) of    the polyester polymer.-   3. The process according to embodiment 1 or 2 further comprising:

disposing the at least one fiber adjacent an internal combustion engine(e.g., under the hood or adjacent the firewall of an automobile, etc.),

wherein the heating is generated by the internal combustion engine.

-   4. The process according to embodiment 1 or 2 further comprising:

manufacturing a textile product comprising the at least one fiber,

wherein the heating comprises washing and/or drying the textile product.

-   5. The process according to embodiment 4, wherein the textile    product is clothing (e.g., a jacket, coat, gloves, footwear, etc.)    or bedding (e.g., a comforter, blanket, sleeping bag, etc.).-   6. A process comprising:

(a) providing a thermoplastic polymer material comprising at least oneor a plurality of polyester polymers and at least one or a combinationof different meltable metal phosphinates; and

(b) melt blowing the thermoplastic polymer material into at least onefiber or a plurality of fibers, with each fiber having a diameter orthickness that is less than about 10 microns,

wherein the metal phosphinate is in an amount that reduces the viscosityof the polyester polymer, and which accelerates, induces or at leastpromotes crystallization of the polyester polymer, when thethermoplastic polymer material is melt blown into the at least onefiber, and the polyester polymer of the at least one fiber is at leastpartially crystalline.

-   7. The process according to embodiment 6, wherein the step of    providing a thermoplastic polymer material comprises:

melt blending of the metal phosphinate with the polyester polymer.

-   8. The process according to embodiment 7, wherein the step of melt    blowing comprises:

extruding the thermoplastic polymer material through at least one or aplurality of corresponding die openings designed (e.g., dimension andshaped) so as to form the at least one fiber.

-   9. The process according to any one of embodiments 1 to 8, wherein    the thermoplastic polymer material comprises a blend of the    polyester polymer and at least one other polymer to form a polymer    blend.-   10. The process according to any one of embodiments 1 to 9, wherein    the polyester polymer is an aliphatic polyester, aromatic polyester    or a combination of an aliphatic polyester and aromatic polyester.-   11. The process according to any one of embodiments 1 to 10, wherein    the thermoplastic polymer material comprises at least about 0.1    percent by weight of the metal phosphinate.-   12. The process according to any one of embodiments 1 to 11, wherein    the thermoplastic polymer material comprises less than about 20    percent by weight of the metal phosphinate.-   13. The process according to any one of embodiments 1 to 12, wherein    the metal phosphinate is a zinc phosphinate.-   14. The process according to any one of embodiments 1 to 13, wherein    the method further comprises melting the thermoplastic polymer    material to form a molten polymer material, and the melt blowing    comprises:

forming (e.g., extruding) the molten polymer material into at least oneor a plurality of fiber preforms; and

solidifying (e.g., cooling) the at least one fiber preform into the atleast one fiber;

wherein the polyester polymer has a melting point and the metalphosphinate melts at or below the melting point of at least thepolyester polymer and functions as a crystallization promoter orcrystallizing agent that causes at least the polyester polymer of themolten polymer material to crystallize before, or at least about thesame time as, the molten polymer material solidifies.

-   15. The process according to any one of embodiments 1 to 14, wherein    the melt blowing is performed at a temperature that causes the    thermoplastic polymer material to reach a temperature less than or    equal to about 360° C.-   16. The process according to any one of embodiments 1 to 14, wherein    the melt blowing is performed at a temperature that causes the    thermoplastic polymer material to reach a temperature in the range    of from at least about 290° C. to less than or equal to about 360°    C.-   17. The process according to any one of embodiments 1 to 16, wherein    the polyester polymer forms the only, a majority, or at least a    substantial polymer portion, i.e., 90%, 85%, 80%, 75% or even 70% by    mass of the thermoplastic polymer material.-   18. The process according to any one of embodiments 1 to 17, wherein    after the melt blowing, the polyester polymer of the thermoplastic    polymer material is completely, mostly, partially, or at least    substantially crystalline.-   19. The process according to any one of embodiments 1 to 18, wherein    enough of the polyester polymer crystallizes that a non-woven web    made of the at least one fiber exhibits less than about 30 percent    linear shrinkage when heated to a temperature of about 150° C. for    about 4 hours.-   20. The process according to any one of embodiments 1 to 18, wherein    enough of the polyester polymer crystallizes that a non-woven web    made of the at least one fiber exhibits less than about 10 percent    linear shrinkage when heated to a temperature of about 150° C. for    about 4 hours.-   21. The process according to any one of embodiments 1 to 20, wherein    the polymer material is melt blown into a fiber exhibiting a low    molecular orientation when compared to the same size melt-spun or    spunbond fiber made with the same polymer material.-   22. The process according to any one of embodiments 1 to 21, wherein    the at least one fiber exhibits a birefringence of less than or    equal to about 0.01.

Method of Making Fibrous Structures Embodiments

-   23. A method of making a fibrous structure, the method comprising:

making fibers using the process according to any one of embodiments 1 to22; and

forming the fibers into a fibrous structure (e.g., a non-woven web,scrim, mat, sheet, or other structures).

-   24. The method according to embodiment 23, wherein the fibrous    structure is operatively adapted (e.g., structurally dimensioned,    shaped, or otherwise configured or designed) for use in an    environment (e.g., adjacent an internal combustion engine, etc.)    where the fibrous structure is exposed to temperatures equal to or    above the T_(g) of the polyester polymer (e.g., a temperature that    is at least about 5° C., 10° C., 15° C., 20° C., 25° C., or even    30° C. above the T_(g)). For example, such a fibrous structure could    be cut or otherwise shaped so as to be secured to the underside of a    hood for an automobile.-   25. The method according to embodiment 23 or 24, wherein enough of    the polyester polymer in each melt blown fiber crystallizes such    that the fibrous structure exhibits less than about 30 percent    linear shrinkage when heated to a temperature of about 150° C. for    about 4 hours.-   26. The method according to embodiment 23 or 24, wherein enough of    the polyester polymer in each melt blown fiber crystallizes such    that the fibrous structure exhibits less than about 10 percent    linear shrinkage when heated to a temperature of about 150° C. for    about 4 hours.

Melt Blown Fiber Embodiments

-   27. At least one melt blown fiber having a diameter or thickness    that is less than about 10 microns and comprising a thermoplastic    polymer material comprising at least one or a plurality of polyester    polymers and at least one or a combination of different meltable    metal phosphinates, wherein the polyester polymer is at least    partially crystalline.-   28. The melt blown fiber according to embodiment 27, wherein the    thermoplastic polymer material comprises a blend of the polyester    polymer and at least one other polymer to form a polymer blend.-   29. The melt blown fiber according to embodiment 27 or 28, wherein    the polyester polymer is an aliphatic polyester, aromatic polyester    or a combination of an aliphatic polyester and aromatic polyester.-   30. The melt blown fiber according to any one of embodiments 27 to    29, wherein the polyester polymer forms the only, a majority, or at    least a substantial polymer portion of the thermoplastic polymer    material.-   31. The melt blown fiber according to any one of embodiments 27 to    30, wherein most or at least a substantial portion of the polyester    polymer of the thermoplastic polymer material is crystalline.-   32. The melt blown fiber according to any one of embodiments 27 to    31, wherein enough of the polyester polymer crystallizes that a    non-woven web of the at least one melt blown fiber exhibits less    than about 30 percent linear shrinkage when heated to a temperature    of about 150° C. for about 4 hours.-   33. The melt blown fiber according to any one of embodiments 27 to    32, wherein enough of the polyester polymer crystallizes that a    non-woven web of the at least one melt blown fiber exhibits less    than about 10 percent shrinkage when heated to a temperature of    150° C. for about 4 hours.-   34. The melt blown fiber according to any one of embodiments 27 to    33, wherein the thermoplastic polymer material comprises at least    about 0.1percent by weight of the metal phosphinate.-   35. The melt blown fiber according to any one of embodiments 27 to    34, wherein the thermoplastic polymer material comprises about 20    percent by weight or less of the metal phosphinate.-   36. The melt blown fiber according to any one of embodiments 27 to    35, wherein the metal phosphinate is a zinc diethylphosphinate.-   37. The melt blown fiber according to any one of embodiments 27 to    36, wherein the melt blown fiber exhibits a low molecular    orientation when compared to the same size melt-spun or spunbond    fiber made with the same polymer material.-   38. The melt blown fiber according to any one of embodiments 27 to    37, wherein the at least one melt blown fiber exhibits a    birefringence of less than or equal to about 0.01.

Fibrous Structure Embodiments

-   39. A fibrous structure (e.g., that is non-woven or woven)    comprising a plurality of the melt blown fiber according to any one    of embodiments 27 to 38.-   40. A fibrous structure comprising a plurality of melt blown fibers,    each melt blown fiber comprising a thermoplastic polymer material    comprising at least one polyester polymer, or a plurality of    polyester polymers, and at least one or a combination of different    meltable metal phosphinates, wherein the at least one polyester    polymer is at least partially crystalline, and the fibrous structure    is operatively adapted (e.g., structurally dimensioned, shaped, or    otherwise configured or designed) for use in an environment (e.g.,    adjacent an internal combustion engine, etc.) where the fibrous    structure is exposed to temperatures equal to or above the T_(g) of    the at least one polyester polymer (e.g., a temperature that is at    least about 5° C., 10° C., 15° C., 20° C., 25° C., or even 30° C.    above the T_(g)). Such a fibrous structure could be configured, for    example, so as to be secured to the underside of a hood for an    automobile.-   41. The fibrous structure according to embodiment 39 or 40, wherein    enough of the at least one polyester polymer in each melt blown    fiber crystallizes such that the fibrous structure exhibits less    than about 30 percent linear shrinkage when heated to a temperature    of about 150° C. for about 4 hours.-   42. The fibrous structure according to embodiment 39 or 40, wherein    enough of the at least one polyester polymer in each melt blown    fiber crystallizes such that the fibrous structure exhibits less    than about 10 percent linear shrinkage when heated to a temperature    of about 150° C. for about 4 hours.-   43. The fibrous structure according to any one of embodiments 39 to    42, wherein the fibrous structure is a non-woven fibrous web.-   44. The fibrous structure according to any one of embodiments 39 or    43, further comprising at least one or a plurality of staple or    otherwise discontinuous fibers, melt spun continuous fibers or a    combination thereof.

Article Embodiments

-   45. An article comprising a fibrous structure according to any one    of the embodiments 39 to 44.

Polymer Composition Embodiments

-   46. A thermoplastic polymer composition comprising at least one or a    plurality of polyester polymers and less than or equal to about 2%    by weight of at least one meltable metal phosphinate or a    combination of different meltable metal phosphinates.-   47. The thermoplastic polymer composition according to embodiment    46, comprising at least about 0.5% by weight of the at least one    meltable metal phosphinate. This is the minimum amount of the metal    phosphinate needed to melt blow 10 micron diameter fibers, when the    composition contains the minimum amount of polyester.

The invention described herein can be used to make halogen free flameretardant polyester melt blown fibrous structures (e.g., fiber webs),and the process used can continuously produce such structures. Thedistribution and dispersion of the flame retardant additives within theblown fibers prevent flame retardant chemicals from being washed orrubbed off from the fiber and web surfaces. The flame retardant blownmicro-fiber webs may be modified to meet different fiber size, weight,density, thickness, loft and functional requirements (e.g., stiffness,resilience, breathability, etc.). In addition to flame retardantproperties, blown micro-fiber webs can be modified to have high thermal,moisture and/or dirt resistance; anti-microbial properties; improvedfiltration properties, etc. Additives other than flame retardants couldbe added during the extrusion process, released into or coated onto theweb or loaded into the web in such forms as fibers or particles. Flameretardant blown micro-fibrous structures may be reprocessed (e.g.,shredded) and used in air-laying processes, or carding and cross-lappingprocesses to make high and medium loft nonwovens.

Fibrous structures of the present invention could be used in a varietyof applications including but not limited to insulation and filtrationapplications. For example, flame retardant or non-flame retardant blownmicro-fibrous structures of this invention may be used as thermalinsulation for occupational apparel, temporary shelters and bedding.Other applications may also include thermal and/or acoustical insulationin vehicles (e.g., automobiles, buses, trucks, trains, aircrafts, boats,ships, etc.), buildings, appliances, or which otherwise meets applicableconstruction codes or manufacturer specifications, filter media, etc.Blown micro-fibrous structures of this invention may become a suitablesubstitute fiber glass structures (e.g., as insulation in internalcombustion engine compartments). Current fiber glass products can bedifficult to handle, compared to the same products made with the fibrousstructures of the present invention. Flame retardant fibrous structuresof this invention may also be a viable substitute for conventional flameretardant type fibrous structures, which are typically expensive andexhibit poor compression resistance and conformability. Suchcharacteristics can be important for fibrous structures used in flameretardant bedding, clothing and temporary shelters.

This invention may take on various modifications and alterations withoutdeparting from its spirit and scope. For example only, the presentinvention could be modified to form fibrous structures that exhibitedone or any combination of a low/high loft, low/high density, andlow/high basis weight. Additives could also be added during extrusion ofthe melt blown fibers or post-processing of the melt blown fibers and/orwebs to make products which are: anti-microbial, moisture resistant,etc. In addition, the melt blown fibrous structures of the currentinvention could be further re-processed into nonwoven media through theuse of air-laying processes. Accordingly, this invention is not limitedto the above description but is to be controlled by the limitations setforth in the following claims and any equivalents thereof.

This invention may be suitably practiced in the absence of any elementnot specifically disclosed herein.

All patents and patent applications cited above, including those in theBackground section, are incorporated by reference into this document intotal.

1. The at least one melt blown fiber according to claim 11, wherein themetal phosphinate is in an amount that at least promotes crystallizationof the polyester polymer, when the thermoplastic polymer material ismelt blown into the at least one melt blown fiber.
 2. The at least onemelt blown fiber according to claim 1 in combination with an internalcombustion engine, wherein the at least one melt blown fiber is disposedadjacent the internal combustion engine such that the at least one meltblown fiber is heated by the internal combustion engine to a temperatureequal to or above the glass transition temperature (T_(g)) of thepolyester polymer.
 3. A textile product comprising the at least one meltblown fiber according to claim
 1. 4. The at least one melt blown fiberaccording to claim 11, wherein the metal phosphinate reduces theviscosity of the polyester polymer and at least promotes crystallizationof the polyester polymer, when the thermoplastic polymer material ismelt blown into the at least one melt blown fiber.
 5. The at least onemelt blown fiber according to claim 1, wherein the thermoplastic polymermaterial comprises in the range of from at least about 0.1 percent byweight of the metal phosphinate up to less than about 20 percent byweight of the metal phosphinate.
 6. (canceled)
 7. The at least one meltblown fiber according to claim 1, wherein the at least one melt blownfiber exhibits a low molecular orientation when compared to the samesize melt-spun or spunbond fiber made with the same polymer material. 8.(canceled)
 9. (canceled)
 10. The fibrous structure according to claim14, wherein enough of the polyester polymer in each melt blown fibercrystallizes such that the fibrous structure exhibits less than about 30percent linear shrinkage when heated to a temperature of about 150° C.for about 4 hours.
 11. At least one melt blown fiber having a diameterof less than about 10 microns and comprising a thermoplastic polymermaterial comprising at least one polyester polymer and at least onemeltable metal phosphinate, wherein said polyester polymer is at leastpartially crystalline.
 12. The at least one melt blown fiber accordingto claim 11, wherein said melt blown fiber exhibits a low molecularorientation when compared to a melt-spun or spunbond fiber made with thesame polymer material.
 13. The at least one melt blown fiber accordingto claim 11, wherein said at least one melt blown fiber exhibits abirefringence of less than or equal to about 0.01.
 14. A fibrousstructure comprising a plurality of said at least one melt blown fiberaccording to claim
 11. 15. A fibrous structure comprising a plurality ofmelt blown fibers, each melt blown fiber comprising a thermoplasticpolymer material comprising at least one polyester polymer, and at leastone meltable metal phosphinate, wherein the at least one polyesterpolymer is at least partially crystalline, and the fibrous structure isoperatively adapted for use in an environment where the fibrousstructure is exposed to temperatures equal to or above the T_(g) of theat least one polyester polymer.
 16. The fibrous structure according toclaim 14, wherein enough of the at least one polyester polymer in eachmelt blown fiber crystallizes such that the fibrous structure exhibitsless than about 10 percent linear shrinkage when heated to a temperatureof about 150° C. for about 4 hours.
 17. A thermoplastic polymercomposition comprising at least one polyester polymer and less than orequal to about 2% by weight of at least one meltable metal phosphinate.18. The at least one melt blown fiber according to claim 12, whereinsaid at least one melt blown fiber exhibits a birefringence of less thanor equal to about 0.01.
 19. A fibrous structure comprising a pluralityof said at least one melt blown fiber according to claim
 12. 20. Afibrous structure comprising a plurality of said at least one melt blownfiber according to claim
 13. 21. The fibrous structure according toclaim 15, wherein enough of the at least one polyester polymer in eachmelt blown fiber crystallizes such that the fibrous structure exhibitsless than about 10 percent linear shrinkage when heated to a temperatureof about 150° C. for about 4 hours.
 22. The at least one melt blownfiber according to claim 4, wherein the at least one melt blown fiberexhibits a low molecular orientation when compared to the same sizemelt-spun or spunbond fiber made with the same polymer material.